Funds are requested to purchase a Special Multi-Laser LSR-2 flow cytometer [Becton-Dickinson] to be placed in the PI's new Flow Cytometry Core in the Center for Regenerative Medicine and Technology [CRMT] opening in 2005. The CMRT is one part of an entirely new 150 million-dollar research building presently under construction in downtown Boston, part of Massachusetts General Hospital [MGH]. Dr. Preffer's Core Cytometry Laboratory will be the only one in the entire new research building or the adjoining MGH. If funded, the requested instrument will serve as the analytic centerpiece to an integrated 5-laser FACSDiVa cell sorting system. The Special Multi-Laser LSR-2 is a six laser instrument and the PI is unaware of any commercially available flow cytometer in the greater metropolitan Boston area similar to it. The PI has recently demonstrated ten-color immunofluorescence capacity and feels the requested instrument will further the aims of the named co-investigators in this application. Due to vast improvements and technological advances in cytometry in recent years, the PI's existing LSR-1 is technologically incapable of the level of performance inherent in the requested instrument. The Department of Pathology Flow Cytometry Core laboratory has served the MGH research community since 1978, and is the only one easily available to all investigators at MGH. For this application, the requested instrument will serve a multidisciplinary group of 18 PIs representing 24 NIH funded grants. The laboratory has a highly skilled operator and PI with a combined 40 years of well documented experience in flow cytometry. The laboratory has administered and sustained itself on a combination of user fees, grants and departmental backing when necessary. The laboratory has the documented financial support of both the Department of Pathology and MGH administration.